Question

What would be the effect on your calculated molar mass of p-dichlorobenzene if your lab partner...

What would be the effect on your calculated molar mass of p-dichlorobenzene if your lab partner left the stopper off the apparatus while you were weighing the solid p-dichlorobenzene?

Explain what would happen if this occurred and how it would affect your result. Your explanation must be mathematical.

Homework Answers

Answer #1

Cyclohexane is fairly volatile, so it would evaporate quickly in an open container. If your partner left the stopper off, it becomes an open container. Effect: The mass of cyclohexane is reduced (lower than believed for the calculations). Effect: The molal concentration of p-dichlorobenzene in cyclohexane is higher than expected. Effect: Since you've got more particles per g of solution than you realized, then your calculated # of particles (the total # that corresponds to the mass of DCB that you weighed out) is higher than it should've been. Effect: More particles / g = smaller molecular weight.

So, your molecular weight determination will give a low result.

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